A standard drill chuck has a chuck body that is mounted on the spindle or arbor of a drill or other similar machine and that is provided externally with a so-called tightening sleeve. A plurality of angularly equispaced jaws are provided between this sleeve and the chuck body which are provided with formations that can move these jaws radially toward each other or radially apart on relative rotation of the tightening sleeve and the chuck body. Normally the jaws are spring-loaded radially outwardly. They are moved radially inwardly when the tightening sleeve is rotated relative to the chuck body by being pushed forward on an inner frustoconical surface of the tightening sleeve.
In order to prevent such a chuck from loosening it is known to provide a ratchet arrangement that normally only allows the tightening sleeve to rotate in the tightening direction on the chuck body. Such arrangements are described in my copending applications Ser. Nos. 011,772 now abandoned and 011,774, now U.S. Pat. No. 4,213,623 issued July 22, 1980 both filed Feb. 13, 1979. In the latter of these applications a ratchet pawl is pivotal about an axis parallel to the chuck axis on a special holding ring clamped to the chuck body. Teeth are formed on the so-called pressure ring that is threaded to the tightening sleeve and that serves to axially fix the tightening sleeve relative to the chuck body. This pawl has a button projecting radially out of the holding ring through a window formed therein and is not only spring loaded into position with its end engaged in the teeth of the pressure ring, but is also so counterbalanced that radially outwardly effective centrifugal force will increase the radial inward force of its tooth into the teeth of the pressure ring.
Such an arrangement has numerous advantages, however, it represents a relatively bulky and trouble-prone structure. The relatively large pawl requires the entire chuck to be built so that it is quite a bit larger and heavier than would normally be necessary. The hole through which the button of the ratchet pawl engages allows shavings and the like produced during use of the chuck to enter its interior, fouling it and requiring eventual cleaning. Furthermore, this button must be held depressed during the entire loosening operation of the chuck to maintain the end of the pawl out of engagement with the ratchet teeth. Holding in this button with one hand while rotating the tightening sleeve to loosen the chuck with the other does not leave the operator another hand to hold the other tool that is being fitted to or taken out of the chuck.